/*  $Id$
**
**  File handling for the wallet client.
**
**  Written by Russ Allbery <rra@stanford.edu>
**  Copyright 2007, 2008 Board of Trustees, Leland Stanford Jr. University
**
**  See LICENSE for licensing terms.
*/

#include <config.h>
#include <system.h>

#include <fcntl.h>

#include <client/internal.h>
#include <util/util.h>

/*
**  Given a filename, some data, and a length, write that data to the given
**  file safely, but overwrite any existing file by that name.
*/
void
overwrite_file(const char *name, const void *data, size_t length)
{
    int fd;
    ssize_t status;

    if (access(name, F_OK) == 0)
        if (unlink(name) < 0)
            sysdie("unable to delete existing file %s", name);
    fd = open(name, O_WRONLY | O_CREAT | O_EXCL, 0600);
    if (fd < 0)
        sysdie("open of %s failed", name);
    status = write(fd, data, length);
    if (status < 0)
        sysdie("write to %s failed", name);
    else if (status != (ssize_t) length)
        die("write to %s truncated", name);
    if (close(fd) < 0)
        sysdie("close of %s failed (file probably truncated)", name);
}


/*
**  Given a filename, some data, and a length, write that data to the given
**  file safely and atomically by creating file.new, writing the data, linking
**  file to file.bak, and then renaming file.new to file.
*/
void
write_file(const char *name, const void *data, size_t length)
{
    char *temp, *backup;

    temp = concat(name, ".new", (char *) 0);
    backup = concat(name, ".bak", (char *) 0);
    overwrite_file(temp, data, length);
    if (access(name, F_OK) == 0) {
        if (access(backup, F_OK) == 0)
            if (unlink(backup) < 0)
                sysdie("unlink of old backup %s failed", backup);
        if (link(name, backup) < 0)
            sysdie("link of %s to %s failed", name, backup);
    }
    if (rename(temp, name) < 0)
        sysdie("rename of %s to %s failed", temp, name);
    free(temp);
    free(backup);
}


/*
**  Given a remctl object, the command prefix, object type, and object name,
**  and a file (which may be NULL), send a wallet get command and write the
**  results to the provided file.  If the file is NULL, write the results to
**  standard output instead.  Returns 0 on success and an exit status on
**  failure.
*/
int
get_file(struct remctl *r, const char *prefix, const char *type,
         const char *name, const char *file)
{
    const char *command[5];
    char *data = NULL;
    size_t length = 0;
    int status;

    command[0] = prefix;
    command[1] = "get";
    command[2] = type;
    command[3] = name;
    command[4] = NULL;
    status = run_command(r, command, &data, &length);
    if (status != 0)
        return status;
    if (data == NULL) {
        warn("no data returned by wallet server");
        return 255;
    }
    if (file != NULL)
        write_file(file, data, length);
    else {
        if (fwrite(data, length, 1, stdout) != 1)
            sysdie("cannot write to standard output");
    }
    return 0;
}